Things are not always as they seem. For example, it might seem obvious that the earth is still and that the sun, moon, planets and stars orbit around it. For thousands of years this is what everyone believed, until Copernicus demonstrated that all the observations astronomers were making were better explained by seeing that the earth and planets orbited around the sun. 

It’s good to be sceptical, to doubt and question things. It was only by questioning the old Ptolemaic model that Copernicus was able to arrive at the much more satisfying and accurate heliocentric model. 

So what can we be certain of? Is there such a thing as total objective, perfect truth? 

Most philosophers will give very sceptical answers. Some will say we can only be sure of the a priori truths of Maths and Logic. That is, things that would still be true even if there was no world in which they occurred.

Of course even philosophers do not live their lives on such a basis. They live as if many things are true even if they cannot prove them to be so.

The seventeenth century French philosopher Rene Descartes considered the question of what he could be sure of and came up with his famous ‘cogito’. He concluded that the only thing he could be sure of was that he was thinking.

It is very hard to prove the existence of an external world (how can you be sure you are not dreaming or hallucinating?) but he could be sure that he was thinking about the questions: hence

Cogito, ergo sum

I think, therefore I am

How to Think for Yourself both follows Descartes and breaks with him.

It follows him in saying that Epistemology, the theory of knowledge, is very problematic. But we can be sure that we think. Therefore it is worthwhile exploring the logical structure of thinking. This leads to the three possible kinds of thinking.

How to Think for Yourself breaks with Descartes by saying that the ‘Cogito’ is not a good starting point for understanding the world. Replacing it with an Actio sidesteps many insoluble problems that the Cogito throws up (see chapters 6 and 7).

For Descartes, the assurance that he could be certain that he was thinking led to assurance of everything else – an external world that behaved in a predictable manner. Most modern philosophers believe Epistemology is more problematic than Descartes made out. 

The findings of modern Physics suggest that reality is not how it appears. The atoms which compose all matter are not ‘solid and indivisible’ but mainly empty space and occupied by very much smaller particles charged with energy. It seems that the same particle can be in two different places at the same time. And so on. 

We can report how the world appears to us but we cannot be sure that that is ‘The Truth’. The same world can appear differently to other beings and from other perspectives. But let us return to the process of thinking.

I think, therefore I am. Who is doing the thinking? I am. There is a Self doing the thinking.

Needless to say Philosophers argue about the nature of the Self – is it illusory? Is it material or immaterial? What is its relationship with a body? 

We do not have to have any definite answers to be able to assert that the very idea of thinking requires some kind of being who is doing or experiencing the thinking, and we may as well call this being a ‘Self’. 

You can take issue with me and deny this, but your very denial is a form of assertion: the existence of an argument needs the existence of two different selves who are able to disagree. 

This is as close as we can get to a basic belief: there is such a thing as thinking and there are beings who do this thinking. 

You may still wish to argue with my assertion, but I can legitimately take your very argument as a confirmation of the validity of what I am saying.